1. Field of Invention
The present invention relates to a system for managing multiple radio modems integrated within a wireless communication device, and more specifically, to a multiradio control system that may enhance multiradio operation by aligning timeslots allocated at a network-level for a wireless communication medium with timeslots allocated at a device-level in the wireless communication device.
2. Background
Modern society has quickly adopted, and become reliant upon, handheld devices for wireless communication. For example, cellular telephones continue to proliferate in the global marketplace due to technological improvements in both the communication quality and device functionality. These wireless communication devices (WCDs) have become common for both personal and business use, allowing users to transmit and receive voice, text and graphical data from a multitude of geographic locations. The communication networks utilized by these devices span different frequencies and cover different transmission distances, each having strengths desirable for various applications.
Cellular networks facilitate WCD communication over large geographic areas. These network technologies have commonly been divided by generations, starting in the late 1970s to early 1980s with first generation (1G) analog cellular telephones that provided baseline voice communication, to modern digital cellular telephones. GSM is an example of a widely employed 2G digital cellular network communicating in the 900 MHZ/1.8 GHZ bands in Europe and at 850 MHz and 1.9 GHZ in the United States. This network provides voice communication and also supports the transmission of textual data via the Short Messaging Service (SMS). SMS allows a WCD to transmit and receive text messages of up to 160 characters, while providing data transfer to packet networks, ISDN and POTS users at 9.6 Kbps. The Multimedia Messaging Service (MMS), an enhanced messaging system allowing for the transmission of sound, graphics and video files in addition to simple text, has also become available in certain devices. Soon emerging technologies such as Digital Video Broadcasting for Handheld Devices (DVB-H) will make streaming digital video, and other similar content, available via direct transmission to a WCD. While long-range communication networks like GSM are a well-accepted means for transmitting and receiving data, due to cost, traffic and legislative concerns, these networks may not be appropriate for all data applications.
Short-range wireless networks provide communication solutions that avoid some of the problems seen in large cellular networks. Bluetooth™ is an example of a short-range wireless technology quickly gaining acceptance in the marketplace. A 1 Mbps Bluetooth™ radio may transmit and receives data at a rate of 720 Kbps within a range of 10 meters, and may transmit up to 100 meters with additional power boosting. Enhanced data rate (EDR) technology also available may enable maximum asymmetric data rates of 1448 Kbps for a 2 Mbps connection and 2178 Kbps for a 3 Mbps connection. A user does not actively instigate a Bluetooth™ network. Instead, a plurality of devices within operating range of each other may automatically form a network group called a “piconet”. Any device may promote itself to the master of the piconet, allowing it to control data exchanges with up to seven “active” slaves and 255 “parked” slaves. Active slaves exchange data based on the clock timing of the master. Parked slaves monitor a beacon signal in order to stay synchronized with the master. These devices continually switch between various active communication and power saving modes in order to transmit data to other piconet members. In addition to Bluetooth™ other popular short-range wireless networks include WLAN (of which “Wi-Fi” local access points communicating in accordance with the IEEE 802.11 standard, is an example), WUSB, UWB, ZigBee (802.15.4, 802.15.4a), and UHF RFID. All of these wireless mediums have features and advantages that make them appropriate for various applications.
More recently, manufacturers have also begun to incorporate various resources for providing enhanced functionality in WCDs (e.g., components and software for performing close-proximity wireless information exchanges). Sensors and/or scanners may be used to read visual or electronic information into a device. A transaction may involve a user holding their WCD in proximity to a target, aiming their WCD at an object (e.g., to take a picture) or sweeping the device over a printed tag or document. Near field communication (NFC) technologies include machine-readable mediums such as radio frequency identification (RFID), Infra-red (IR) communication, optical character recognition (OCR) and various other types of visual, electronic and magnetic scanning are used to quickly input desired information into the WCD without the need for manual entry by a user.
Manufacturers continue to incorporate as many of the previously discussed exemplary communication features as possible into wireless communication devices in an attempt to bring powerful, “do-all” devices to market. Devices incorporating long-range, short-range and NFC resources often support multiple mediums in each category. This may allow a WCD to flexibly adjust to its surroundings, for example, communicating both with a WLAN access point and a Bluetooth™ communication accessory, possibly at the same time.
Given the large array communication features that may be compiled into a single device, it is foreseeable that a user will need to employ a WCD to its full potential when replacing other productivity related devices. For example, a user may utilize a fully-functioned WCD to replace traditional tools such as individual phones, facsimile machines, computers, storage media, etc., which tend to be cumbersome to both integrate and transport. In one scenario, a WCD may communicate simultaneously over a plurality of different wireless mediums. A user may utilize multiple peripheral Bluetooth™ devices (e.g., a headset, keyboard, etc.) while having a voice conversation over GSM and interacting with a WLAN access point in order to access the Internet. Problems may occur when these communications interfere with each other. Even if wireless communication mediums do not have identical operating frequencies, a radio modem may cause extraneous interference to another medium. Further, it is possible for the combined effects of two or more concurrently operating radios to create intermodulation in another bandwidth due to harmonic effects. These disturbances may cause errors resulting in the required retransmission of lost packets, and the overall degradation of performance for one or more communication mediums.
Evolving strategies for regulating air time between two or more radio modems contained in the same device often require a centralized (as a single component or distributed among various components) communication control enforcing an operational schedule for all wireless activity, the regulation of which helps to reduce potential communication collisions between active radio modems. However, in order for an operational schedule to be effective, the interplay of radio modem activity must be precisely controlled. Precision may be derived from the communication control being synchronized with the modems by, for example, knowing the communication backlog and timing patterns of the active radio modems.
While centrally-controlled wireless resource management may be effective in optimizing some wireless communication mediums, other wireless mediums may continue to be problematic. For example, wireless protocols that are enabled for carrying synchronous data may operate in a mode that uses fixed transmission and reception intervals, like GSM and Bluetooth™, may be more readily managed by a centralized controller because a schedule may be precisely defined without requiring large buffer time periods. However, other wireless mediums are not so predictive (e.g., WLAN). These unscheduled wireless mediums must compete for available transactional timeslots, and as a result, may require longer execution time to allow for determination of carrier availability. These determination periods, or contention periods, add to the time needed to complete a transaction wherein both a message frame is sent and also an acknowledgement frame must be received. If both of these frames are not sent/received in the time available, the message is considered a failure, which may waste time in two ways: time is wasted by the failed WLAN message attempt (this time could have been successfully used by another wireless medium), and further, time is wasted in attempting to transmit the WLAN message again, which may also fail. Further, due to the dynamic nature of these contention periods there is no absolute way for predicting how long a certain contention period will last before access to the wireless medium is obtained, so the time needed for transmitting certain packet cannot be defined beforehand, which makes it difficult to provide an operational schedule for such a wireless medium.